1. Field of the Invention
The present invention relates to devices for measurement of human impairment, which might occur as the result of low-level alcohol or drug exposure and hangovers among other physiological factors, and more particularly to a handheld fitness for duty (FFD) tester which adapts for human learning during the test and determines a test score which may be used to determine the test subject's fitness for duty.
The definition of FFD tests are well-documented by Burns and Hiller-Sturmhofel ("Alcohol's Effect on Cognition", Alcohol World Health & Research, Vol. 19, No. 2, 1995), but to date, no suitable instrument has been available to accomplish these tasks. The performance criteria for such an instrument include sensitivity to small changes in blood alcohol concentration (BAC), detection of concentrations of BAC below 0.05 percent, reliable and repeatable results, ease and simplicity of test administration, reasonable price, adjustment for learning when a test subject uses the device on a routine basis, establishment of a baseline for each person tested, providing a comparison against a database of similar individuals, updating each individual's baseline to account for learning, and measurement of job or safety-related skills.
Significant work has been carried out by Jonathan Howland, et al. at Boston University School of Public Health which indicates significant performance effects for low-level alcohol exposure (0.04 gm % BAC) for persons performing on diesel engine and ship bridge control simulators ("A Random Trial on the Effects of Alcohol on Safety Sensitive Occupational Performance: Simulated Merchant Ship Handling" (Draft), Jul. 6, 1998). Howland's preliminary findings tend to confirm earlier Boston University survey data from the workplace drinking study ("Employee Attitudes Towards Work-Site Alcohol Testing", JOEM, Vol. 38, No. 10, October 1996) which indicate an association between drinking alcohol at lunch (low-level exposure) and workplace performance impairment or safety problems. Studies using flight simulators, automobile simulators, and industrial task simulation also indicate impairment due to low-level intoxication or hangovers. Furthermore, research appears to indicate that neither the exposed subjects nor their co-workers are aware of this impairment.
From a safety management perspective, these findings pose problems because the effects of low-level alcohol exposure and hangovers are difficult to detect for at least two reasons. First, detection is difficult because affected workers and their co-workers are unable to discern impairment at low-levels of exposure, and secondly, alcohol may have residual impairing effects even when BAC is zero.
Managers in industry, commerce, and government are very much in need of a system that will effectively and efficiently evaluate an employee's fitness for duty without intrusive testing, and regardless of cause (e.g. alcohol, illegal drugs, lack of sleep, or side-effects of prescribed medication). Such an FFD testing system would have application to a broad range of industrial settings involving safety-sensitive work such as aircraft pilots and mechanics, nuclear power plant workers, train engineers, truck drivers, aircraft controllers, ship bridge or engineering personnel, or surgeons.
Finding a rapid and simple FFD device or test would potentially have broad application in these safety-sensitive industries, and could solve the problem of detection and confirmation with employees of any low-level impairment without unduly exposing either the employer or employee to legal liability for the testing procedure or accidents resulting the low-level impairment. Such a system could possibly facilitate self-imposed behavior modifications or seeking of substance abuse counseling by employees who repeatedly fail to pass the FFD test.
The commercial applications of such a FFD test are very large, and present a significant market in response to high, pent-up demand for such a device by the airlines, railroads, trucking companies, and ship operators, among other industries and commercial or governmental organizations.
2. Description of the Related Art
The use of a pressure plate was considered to determine neuromuscular responses. U.S. Pat. No. 4,195,643 discloses a pressure plate for testing lameness of horses suffering from arthritis, septic tendinitis, and hair-line fractures. The device uses time and frequency-domain analysis to determine physiological conditions of the animal under test. A block diagram of this approach is shown in FIG. 1.
U.S. Pat. No. 5,388,591 expands the application of the pressure plate to the analysis of the human postural control system by employing statistical analysis of the random displacement of the center of pressure of the subject while standing on the pressure plate, as depicted in FIG. 2.
Although use of a pressure plate may initially appear useful for FFD testing, there are drawbacks to its use. From a safety perspective, requiring a subject to stand on a platform 40 cm by 40 cm which is several centimeters high may create a potentially unsafe condition, particularly if the individual under test has poor balance due to drug or alcohol impairment, poor health, or other physiological factors. This problem may be exacerbated if the subject is asked to balance on one foot to perform a test having the greatest sensitivity to balance. In addition, the pressure plate does not have a means to "push" the subject to higher levels of work effort; the pressure plate test is simply a measure of balance.